Evaluation of Hydrogen Absorption and Desorption for Ti-6Al-4V Alloy with Low Activation Property as a Vacuum Vessel Material

The hydrogen absorption and desorption properties of Ti-6Al-4V alloy were evaluated under the conditions of fusion reactor operation. When the hydrogen pressure and the temperature were kept at 0.3 Pa and 660K, respectively, for 48 h, the amount of absorption for the polished sample was almost the same as the initial concentration of hydrogen (90ppm). At a higher pressure, 10 Pa, the amount of absorption increased when the temperature exceeded 750 K. In the case of the degassed sample, the amount of absorption changed irregularly in the temperature range from 600 K to 650 K which was 100 K higher than that of pure α-Ti. The amount of absorption saturated in the absorption time of about 20 h at 660 K. The saturation level was less than 250ppm which was lower than the critical concentration for the embrittlement of Ti-6Al-4V alloy (1000ppm).